<template>
  <div class="container">
    <!-- 固定导航 -->
    <van-nav-bar
      fixed
      left-arrow
      @click-left="$router.back()"
      title="小思同学"
    ></van-nav-bar>

    <!-- 聊天主体区域 -->
    <div class="chat-list">
      <div v-for="(obj, index) in chatList" :key="index">
        <!-- 左侧是机器人小思 -->
        <div class="chat-item left" v-if="obj.name === 'xs'" ref="chat-item">
          <van-image
            fit="cover"
            round
            src="https://img.yzcdn.cn/vant/cat.jpeg"
          />
          <div class="chat-pao">{{ obj.msg }}</div>
        </div>

        <!-- 右侧是当前用户 -->
        <div class="chat-item right" v-if="obj.name === 'me'" ref="chat-item">
          <div class="chat-pao">{{ obj.msg }}</div>
          <van-image fit="cover" round :src="userInfo.photo" />
        </div>
      </div>
    </div>

    <!-- 对话区域 -->
    <div class="reply-container van-hairline--top">
      <van-field
        v-jujiao
        placeholder="说点什么..."
        v-model.trim="txt"
        @keydown.enter="sendMsgFn"
      >
        <!-- native: 当给一个组件加事件的时候 -->
        <template #button>
          <span style="font-size: 12px; color: #999" @click="sendMsgFn"
            >提交</span
          >
        </template>
      </van-field>
    </div>
  </div>
</template>

<script>
import { mapState } from "vuex";
// 导入 socket.io-client 包
import { io } from "socket.io-client";
import { Notify } from "vant";

let socket = null;
export default {
  name: "Chat",
  data() {
    return {
      chatList: JSON.parse(window.localStorage.getItem("chatList")) || [
        // 只根据 name 属性，即可判断出这个消息应该渲染到左侧还是右侧
        { name: "xs", msg: "Hi，我是小思，我能帮你什么呢" },
        { name: "me", msg: "我是编程小王子，我要找老板加薪" },
      ],
      txt: "",
    };
  },
  created() {
    // 1. 连接服务器
    // 创建客户端 websocket 的实例
    socket = io("http://toutiao.itheima.net", {
      query: {
        token: this.token,
      },
      transports: ["websocket"],
    });
    // 2. 监听连接成功事件
    socket.on("connect", () => {
      // 4. 监听
      socket.on("message", (data) => {
        console.log(data);

        this.chatList.push({
          name: "xs",
          msg: data.msg,
        });
        // 异步更新
        this.$nextTick(() => {
          this.scrollIntoView();
        });
      });
    });
  },
  methods: {
    sendMsgFn() {
      if (!this.txt) {
        Notify({ type: "warning", message: "消息内容不能为空" });
        return;
      }
      // 3. 发送消息
      socket.emit("message", {
        msg: this.txt,
        timestamp: Date.now(),
      });
      this.chatList.push({
        name: "me",
        msg: this.txt,
      });
      // 异步更新
      this.$nextTick(() => {
        this.scrollIntoView();
      });
      this.txt = "";
    },
    // 让最后一个 chat-item 滚动到 视口范围内
    scrollIntoView() {
      // 获取所有的 chat-item dom元素
      const chatItems = this.$refs["chat-item"];
      // 找到最后一个
      const chatItem = chatItems[chatItems.length - 1];
      // 让最后一个chat-item 滚动到视口
      chatItem.scrollIntoView({
        behavior: "smooth",
      });
    },
  },
  destroyed() {
    //   console.log('切走了');

    socket && socket.close();
  },
  watch: {
    chatList(newVal) {
      window.localStorage.setItem("chatList", JSON.stringify(newVal));
    },
  },
  computed: {
    ...mapState(["userInfo"]),
  },
};
</script>

<style lang="less" scoped>
.container {
  height: 100%;
  width: 100%;
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  background: #fafafa;
  padding: 46px 0 50px 0;
  .chat-list {
    height: 100%;
    overflow-y: scroll;
    .chat-item {
      padding: 10px;
      .van-image {
        vertical-align: top;
        width: 40px;
        height: 40px;
      }
      .chat-pao {
        vertical-align: top;
        display: inline-block;
        min-width: 40px;
        max-width: 70%;
        min-height: 40px;
        line-height: 38px;
        border: 0.5px solid #c2d9ea;
        border-radius: 4px;
        position: relative;
        padding: 0 10px;
        background-color: #e0effb;
        word-break: break-all;
        font-size: 14px;
        color: #333;
        &::before {
          content: "";
          width: 10px;
          height: 10px;
          position: absolute;
          top: 12px;
          border-top: 0.5px solid #c2d9ea;
          border-right: 0.5px solid #c2d9ea;
          background: #e0effb;
        }
      }
    }
  }
}
.chat-item.right {
  text-align: right;
  .chat-pao {
    margin-left: 0;
    margin-right: 15px;
    &::before {
      right: -6px;
      transform: rotate(45deg);
    }
  }
}
.chat-item.left {
  text-align: left;
  .chat-pao {
    margin-left: 15px;
    margin-right: 0;
    &::before {
      left: -5px;
      transform: rotate(-135deg);
    }
  }
}
.reply-container {
  position: fixed;
  left: 0;
  bottom: 0;
  height: 44px;
  width: 100%;
  background: #f5f5f5;
  z-index: 9999;
}
</style>
